A grid fin is commonly used on aircraft, missiles and bombs as a flight control surface in place of planar fins. The grid fin has walls forming one or a plurality of passages that are exposed to rapidly flowing air. The walls of the grid fin passages are made to have a precise shape, a light weight, and a high strength and stiffness. A method for constructing at low cost, such an article with one or a plurality of passages, especially for grid fins, and the article itself, would be of value.